The invention is related to the foundation work of civil engineering and architecture (construction) engineering especially referring to the fabrication and utilization of reverse circulation drillingtyped foundation piles which are suitable for deep foundation works.
The traditional fabrication method of cast-in-place hollow piles formed by reverse circulation drilling method uses pipe-shaped steel molds to confine concrete grout for making the interior hollow. This method is not practical for deep foundation works as it is hard to control appropriate time for taking mold apart because of difference of depth, difference of pressure and change of temperature. If the mold is taken apart before solidification, the whole piece may be collapsed. If the mold is taken apart after solidification, the pile is usually broken.
After study and test, the applicant provides an idea that sands are poured in the central hollow part to have the same pressure as that of the surrounding concrete grout. Upon solidification of concrete grout, sands are suctioned out to complete a hollow pile.